Thanks for the info Nicolas! I look forward to give this service a try, even if it's a pity it doesn't run 24-hours a day for those 6.30 am flights. During the day I usually use the train + Roissybus combo which I find quite convenient (or RER A to Cergy + 95.18 bus for the cheapest ride to Roissy).

Wow, that is really helpful, especially as two of the stops are my clients!

Have you taken the bus before? Do you know if it goes directly to the airport or if it stops at the other locations in La Defense? I went ahead and booked it because it sounded like such a great value, but I have two problems with it already:

1) the reservation form doesn't work in Google Chrome
2) they don't tell you until after you have paid that "Vous recevrez 30 mn avant votre départ, un sms vous précisant l'horaire exact de passage votre navette au point Cielos choisi. En fonction du nombre de points de prise en charge, cet horaire pourra varier de 0 à 15mn par rapport à l’horaire choisi. Nous vous prions de vous présenter au point Cielos, quelques minutes avant l’horaire confirmé par sms." (for non French speakers - basically they will text you 30mn before the time you booked, and let you know exactly what time to show up, within 15mn of your booked time. Which is not very convenient if you are trying to catch a flight on a tight timetable or book meetings before your shuttle - and I am doing both!)